Vol. 36, No. 2
ANTIMICROBIAL AGENTS AND CHEMOTHERAPY, Feb. 1992, p. 440-445 0066-4804/92/020440-06$02.00/0 Copyright C) 1992, American Society for Microbiology
Characterization of Four 13-Lactamases Produced by Staphylococcus aureus DEBORAH J. ZYGMUNT,1 CHARLES W. STRATTON,"12 AND DOUGLAS S. KERNODLEl.3* Division of Infectious Diseases, Department of Medicine,' and Department of Pathology,2 Vanderbilt University School of Medicine, Nashville, Tennessee 37232, and Medical Service, Department of Veterans Affairs Medical Center, Nashville, Tennessee 372123 Received 27 June 1991/Accepted 7 November 1991
Staphylococcus aureus produces four types of ,-lactamase (A, B, C, and D). To investigate the effect of specific I-lactamase type upon staphylococcal resistance, each P-lactamase was purified to homogeneity, and the Michaelis constants (Km values) and turnover numbers (kcat values) for various penicillin and cephalosporin substrates were determined. Whereas Km values of the four 3-lactamases were comparable for penicillin G, cephalothin, and cefamandole, the type A and D enzymes exhibited greater affinity than the type B and C 13-lactamases for nitrocefin, cefazolin, and cephapirin. Conversely, the type B and C 1-lactamases exhibited greater kcat values than the type A and D enzymes against most of the cephalosporin agents, excluding nitrocefin. In contrast to earlier reports suggesting that the type B ,3-lactamase is relatively inefficient in hydrolyzing penicillin G, we found only minor differences in the specific activities and k
ANTIMICROBIAL AGENTS AND CHEMOTHERAPY, Feb. 1992, p. 440-445 0066-4804/92/020440-06$02.00/0 Copyright C) 1992, American Society for Microbiology
Characterization of Four 13-Lactamases Produced by Staphylococcus aureus DEBORAH J. ZYGMUNT,1 CHARLES W. STRATTON,"12 AND DOUGLAS S. KERNODLEl.3* Division of Infectious Diseases, Department of Medicine,' and Department of Pathology,2 Vanderbilt University School of Medicine, Nashville, Tennessee 37232, and Medical Service, Department of Veterans Affairs Medical Center, Nashville, Tennessee 372123 Received 27 June 1991/Accepted 7 November 1991
Staphylococcus aureus produces four types of ,-lactamase (A, B, C, and D). To investigate the effect of specific I-lactamase type upon staphylococcal resistance, each P-lactamase was purified to homogeneity, and the Michaelis constants (Km values) and turnover numbers (kcat values) for various penicillin and cephalosporin substrates were determined. Whereas Km values of the four 3-lactamases were comparable for penicillin G, cephalothin, and cefamandole, the type A and D enzymes exhibited greater affinity than the type B and C 13-lactamases for nitrocefin, cefazolin, and cephapirin. Conversely, the type B and C 1-lactamases exhibited greater kcat values than the type A and D enzymes against most of the cephalosporin agents, excluding nitrocefin. In contrast to earlier reports suggesting that the type B ,3-lactamase is relatively inefficient in hydrolyzing penicillin G, we found only minor differences in the specific activities and k
